Secondary or Auxiliary Fans are smaller, portable fans used to supplement the primary fan ventilation. Auxiliary fan and duct systems may be either forcing systems where fresh air is pushed into mine headings or exhausting systems that draw out contaminated air. Auxiliary Fans are installed underground for ventilating mines that are not adequately ventilated by the air current produced by the primary mine ventilation fans. They are driven by compressed air or electricity. Secondary or auxiliary fans can be Axial, Centrifugal or Mixed Flow Fans:
- Axial Fans: Variable and fixed Pitch Fans
- Centrifugal Fans: High Efficiency Airfoil and Backward Curved Fans
- Mixed Flow Fans
